The game

Nine holes, par 36 and 2,990 metres, played from behind the ball with a wireframe perspective view and a plan view beside it. It is from 1983 and it is written entirely in BASIC.

The turn

Every shot goes through three chained screens, all on the same button:

1. The club (subroutine 1000). Thirteen: three woods, seven irons, the pitching wedge, the sand wedge and the putter. The pad cycles round.
2. The direction (subroutine 1100). Degrees, five at a time with left and right and ninety at a time with up and down. The lower compass needle follows along.
3. The power (subroutine 1200). A bar that rises and falls on its own eight pixels at a time; the button freezes it. The higher it stops, the harder the shot: the sum is PW=INT((192-PW)/9), giving 0 to 20. Behind it, line 230 takes one off and will not go below 2.

What decides where it lands

The launch speed is the power times the club's factor - 250 for the driver, 85 for the putter - plus the wind's head-or-tail component. The perpendicular component is kept separately as side spin, and on every pass of the flight it bends the angle a little: that is why shots curve.

The wind is drawn once per hole (subroutine 9060): any direction from 0 to 359 and a strength from 1 to 9. Within a hole it never changes.

The flight is an ordinary projectile with gravity 9.8083 and fixed time steps of 0.4. When the height goes negative the ball bounces: it keeps 40 % of the speed and 70 % of the angle. With a launch angle under 8 - a putt or a low shot

• it does not simulate the arc at all: it works out where it lands in one go

and keeps 85 % of the speed.

The terrain

The game has no terrain map: it asks the screen. Line 380 takes the ball's position over to the plan view in the right-hand panel and reads with POINT whatever colour is painted there. That colour IS the terrain:

colour	terrain	what happens
0	rough	rough stance, no penalty
1	the hole	putting stance
2	the fairway	normal stance
3	the green	putting stance
4	water	two strokes and a drop nearby
6	out of bounds	two strokes and a drop nearby
13	a tree	slows sharply and keeps bouncing under it
14	a bunker	sand stance, and it stops dead

When a drop is needed (subroutine 3000), the game searches in circles of growing radius - fifteen at a time, twenty-four points per turn - until it finds a valid colour.

Rules that live in the code, not the manual

• The driver only from the tee. If the ball is not on the tee and you had picked the 1W, line 235 swaps it for the 3-wood.
• The putter in a bunker does not strike. Line 280 sends the turn back to the start... and passing through line 225 again adds another stroke. Trying it costs a stroke every time.
• Shots from sand depend on the club. With a wood the distance is drawn at random between 50 and 200; with the pitching or sand wedge, between 75 and 100 % of normal; with any other iron, 60 % and a lot of sideways spread.
• The round is played once. The program never issues a RESTORE, and the pointer that reads the course does not rewind either: after hole 9, line 720 is a GOTO 720, an infinite loop. The only way out is a reset.

The course

hole	par	dist.	bunkers	water	trees
1	4	373 m	4	-	2
2	3	155 m	2	-	2
3	4	332 m	2	yes	1
4	5	441 m	2	yes	1
5	4	376 m	1	yes	1
6	4	365 m	1	yes	1
7	4	328 m	1	yes	2
8	3	138 m	1	yes	2
9	5	482 m	1	yes	2

Hole 2 is the only one with no fairway: tee straight to green. And holes 1 and 2 are the only ones without water. The pars add up to 36, which is the total the scoreboard writes by hand in line 7530.